Randomized controlled study of human zona pellucida dissection using the zona infrared laser optical system: evaluation of blastomere damage, embryo development, and subsequent hatching.

OBJECTIVE To assess the effect of laser hatching on human embryo damage and subsequent development using the Zona Infrared Laser Optical System (ZILOS). DESIGN Randomized controlled study. SETTING Tertiary care fertility clinic. PATIENT(S) One hundred fourteen donated and discarded frozen human embryos. INTERVENTION(S) Embryos were thawed, cultured with cleavage and morphology evaluated periodically, and randomized into control, partial hatching, or complete hatching groups. The laser hatching procedure was performed by ZILOS. Zona thickness and embryo diameter were recorded. Complete hatching involved the production of a full-thickness defect in the zona and partial hatching, a defect in the outer half of the zona. No laser treatment was administered to the control group. MAIN OUTCOME MEASURE(S) Blastocyst development and completion of hatching process. RESULT(S) No significant difference was noted between the three study groups for their baseline characteristics. There was no significant difference in blastocyst development among the three groups. However, the complete hatching group showed a significant increase in hatching compared to the control group. CONCLUSION(S) Complete laser hatching of human embryos using the ZILOS does not have an adverse effect on subsequent development and increases the rate of completion of hatching.

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